Filter including randomly-oriented fibers for reduction of particle breakthrough

ABSTRACT

Provided is a cigarette filter and method of making the filter. The filter includes an adsorbent dispersed within the filter and a downstream plug of randomly-oriented fibers. The randomly-oriented fibers mechanically capture adsorbent particles entrained in tobacco smoke. One or more plugs of axially-oriented fibers may also be located upstream and/or downstream of the adsorbent, and are included in an amount sufficient to adjust the length of the filter.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. provisional Application No. 61/008,305, filed on Dec. 20, 2007, the entire content of which is incorporated herein by reference.

BACKGROUND

Cigarettes typically comprise filter elements that may have adsorbent materials, such as carbon, incorporated therein. Filter elements adapted to be incorporated in a filter cigarette may comprise, for example, particles or granules of carbon, such as activated carbon or activated charcoal and/or other adsorbent materials, incorporated within the cellulose acetate tow or in cavities between cellulose acetate material.

SUMMARY

Provided is a filter assembly for a smoking article having reduced adsorbent particle breakthrough. The filter assembly comprises an adsorbent including smoke entrainable adsorbent particles contained within the filter and a plug including randomly-oriented fibers located downstream of the adsorbent. The plug including randomly-oriented fibers provides reduced adsorbent particle breakthrough.

In a preferred embodiment, the filter assembly is a plug-space-plug filter. Most preferably, the plug of randomly-oriented fibers is located downstream of the adsorbent. Preferably, the plug of randomly-oriented fibers is located immediately downstream of the adsorbent.

In an embodiment, a plug of axially oriented fibers is located upstream of the adsorbent. In yet another embodiment, a plug of axially oriented fibers is located downstream of the adsorbent.

In a preferred embodiment, the filter assembly contains a plug of randomly-oriented fibers having a length of about 3 mm to about 10 mm. One or more plugs of axially-oriented fibers can be added to adjust the length of the filter. However, in an embodiment, no axially-oriented fibers are included in the filter.

In a preferred embodiment, the filter assembly mechanically reduces adsorbent particle breakthrough.

Also provided is a smoking article including a filter assembly that reduces and/or eliminates adsorbent particle breakthrough in mainstream smoke.

In a preferred embodiment, the smoking article includes a tobacco rod and a filter assembly. Preferably, the filter assembly is a plug-space-plug filter, wherein the space is filled with an adsorbent. In a preferred embodiment, a plug of randomly-oriented fibers is located downstream of the space (cavity) filled with the adsorbent. In a preferred embodiment, the tobacco rod includes tobacco material and a wrapper. Preferably, the filter assembly is attached to one end of the tobacco rod with tipping paper.

Also provided is a method of making a filter assembly for smoking articles that provides reduced and/or eliminated adsorbent particle breakthrough in tobacco smoke.

In a preferred embodiment, the method includes filling a cavity of a plug-space-plug filter assembly with an adsorbent, wherein the cavity is bordered by a plug of randomly-oriented fibers and a plug of cellulose acetate. In another embodiment, the cellulose acetate plug is a plug of axially oriented fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art plug-space-plug filter for a smoking article.

FIG. 2 illustrates an embodiment of a plug-space-plug filter including a plug of randomly-oriented fibers.

FIG. 3 illustrates a second embodiment of a plug-space-plug filter including a plug of randomly-oriented fibers.

FIG. 4 illustrates a third embodiment of a plug-space-plug filter including a plug of randomly-oriented fibers.

FIG. 5 illustrates a partially unwrapped smoking article including a plug-space-plug filter including a plug of randomly-oriented fibers.

DETAILED DESCRIPTION

Disclosed is a filter adapted to be incorporated into a smoking article such as a filter cigarette. The filter comprises filter material that includes randomly-oriented fibers. To the extent that adsorbent particles or fragments of adsorbent particles could possibly be entrained in mainstream smoke and issue through (i.e., breakthrough) the mouth end of the cigarette, the randomly-oriented fibers mechanically trap adsorbent particles entrained in mainstream smoke.

As used herein, the terminology “smoke entrainable particles” describes beads, granules, dust, fines, powders and the like having a size of about 0.1 micron to about 10 microns, which may become entrained in mainstream smoke.

As used herein, the term “randomly-oriented fibers,” “plug of randomly-oriented fibers” and/or “randomly-oriented” describes woven and non-woven fibers including tangled continuous filaments oriented in various directions that are not substantially parallel to the flow of mainstream smoke as it passes through a smoking article. In contrast, axially oriented fibers in a filter plug are substantially parallel to the flow of mainstream smoke, and are formed in a continuous tow band running on the axial direction with minimum entanglement. “Randomly-oriented fibers,” “plug of randomly-oriented fibers” and/or “randomly-oriented” also describe non-woven materials that can be made using dry laid or wet laid processes including point bound, spun bound, needle felt, needle punch, suspension in water, etc. Details of manufacturing techniques for making filter rods having randomly oriented fibers can be found in U.S. Pat. Nos. 3,111,702, 4,540,625 and 5,817,159, the disclosures of which are incorporated herein by reference.

Preferably, the filter is adapted to be incorporated in a filter cigarette. Cigarette filters are made in a variety of designs. Typically, cigarette filters comprise four main components: a filter tow such as a bundle of cellulose acetate fibers or paper that comprise the bulk of the filter; a plasticizer (i.e., a softening agent added to bind the filter fibers together into a continuous filter rod); a plug wrap (i.e., a paper wrapper that is used to contain the filter material); and an adhesive used to secure the plug wrap to the continuous filter rod.

Filter rods for making cigarette filters, which can be attached to tobacco rods (e.g., attached with tipping paper) to produce filter cigarettes, can be made by forming a bundle or tow of filter material into a rod using a rod forming apparatus. Typically, a filter rod comprises up to thirty thousand filaments of filter material. A preferred filter material used to form a filter rod is cellulose acetate, which is a cellulose ester.

A plasticizer or binder such as triacetin is added to the tow before it is passed into the rod forming apparatus. Furthermore, the tow can be spread and fluffed up, or “bloomed,” usually by placing the tow under tension and passing it over air jets. The bloomed tow can be passed through a funnel or other constricting device and then through a shaped aperture to form the filter rod.

The plasticizer, which can be added to the tow during or after blooming, can enhance the bonding of the filaments to each other at their cross-over points when the tow is gathered. Thus, addition of a plasticizer can increase the firmness of the filter rod formed from the tow. The plasticizer may also have filtration properties. The attributes of the finished filter rod (e.g., filtration efficiency, firmness, dimensional stability, etc.) can be improved by curing (e.g., heating) the plasticizer.

Various filter constructions can be used to form the filter element. Exemplary filter structures include, but are not limited to, a mono filter, a dual filter, a triple filter, a cavity filter, a recessed filter, a free-flow filter or combinations thereof. Mono filters typically contain cellulose acetate tow or cellulose paper materials. Mono cellulose filters or paper filters can be effective filters for tar and/or nicotine. Dual filters typically comprise a cellulose acetate mouth end and a pure cellulose or cellulose acetate segment. The length and pressure drop of the segments in a dual filter can be adjusted to provide the desired filtration (i.e., adsorption and/or absorption) and resistance to draw (RTD).

The filter element can be attached to a tobacco rod to form a filter cigarette. In production of a cigarette, a cut filler composition can be combined with other cigarette additives and provided to a cigarette-making machine to produce a tobacco column, which is then wrapped in cigarette paper to form a tobacco rod that is cut into sections, and optionally tipped with a filter. The resulting cigarettes can be manufactured to desired specifications using standard or modified cigarette making techniques and equipment. Cigarettes may range from about 50 mm to about 120 mm in length. The circumference is typically from about 15 mm to about 30 mm, preferably around 25 mm. The tobacco packing density is typically between the range of about 100 mg/cm³ to about 300 mg/cm³, and preferably 150 mg/cm³ to about 275 mg/cm³.

Tobacco cut filler is normally in the form of shreds or strands cut into widths ranging from about 1/10 inch to about 1/20 inch or even 1/40 inch. The lengths of the strands range from between about 0.25 inches to about 3 inches. The cigarettes may further comprise one or more flavorants or other additives (e.g., burn additives, combustion modifying agents, coloring agents, binders, etc.).

Any suitable tobacco mixture may be used for the cut filler. Examples of suitable types of tobacco materials include flue-cured, Burley, Bright, Maryland or Oriental tobaccos, the rare or specialty tobaccos, and blends thereof. The tobacco material can be provided in the form of tobacco lamina, processed tobacco materials such as volume expanded or puffed tobacco, processed tobacco stems such as cut-rolled or cut-puffed stems, reconstituted tobacco materials, or blends thereof. The tobacco can also include tobacco substitutes.

The term “mainstream” smoke refers to the mixture of gases passing down the tobacco rod and issuing through the filter end, i.e., the amount of smoke issuing or drawn from the mouth end of a cigarette during smoking of the cigarette. The mainstream smoke contains smoke that is drawn in through both the lighted region, as well as through the cigarette paper wrapper. The term “side stream” smoke refers to smoke produced during static burning.

Prior art plug-space-plug carbon filters 105, as illustrated in FIG. 1, include a bed 115 of an adsorbent 112, such as activated carbon, between plugs 130 of axially oriented fibers. Typically, the axially oriented fibers are cellulose acetate fibers. Not wishing to be bound by theory, as smoke is drawn downstream through the filter, some smoke entrainable particles, dust, and/or fines might penetrate channels between the individual fibers and/or migrate along the fibers resulting in adsorbent particle breakthrough of the filter. In a preferred embodiment, the plug-space-plug filter 105 is attached to a tobacco rod 160 that is wrapped with wrapping paper 170 to form a smoking article 100. Tipping paper 165 surrounds the filter 105 and a portion of the tobacco rod 160.

As described herein, a filter assembly for a smoking article produces potentially reduced and/or eliminated adsorbent particle breakthrough by improving the mechanical capture of smoke entrainable particles.

In a preferred embodiment, the filter assembly 10 is a plug-space-plug oriented filter assembly. As seen in FIG. 2, preferably, the filter assembly 10 is a plug-space-plug filter. Preferably, a portion of an adsorbent 12, including smoke entrainable particles, is located in the inner cavity 15 of the filter 10, and a plug 16 of randomly-oriented fibers 14 is located downstream to reduce adsorbent particle breakthrough as mainstream smoke passes through the filter assembly 10. In theory, because the fibers 14 are not axially aligned, the adsorbent particles do not travel through the channels between the fibers or along the fibers, thereby reducing or eliminating adsorbent particle breakthrough in mainstream smoke.

In a preferred embodiment, the adsorbent and/or smoke entrainable particles include any suitable adsorbent media. Exemplary adsorbents include molecular sieves such as zeolites, silicas, silicates, aluminas, and/or carbons (e.g. activated carbon). A preferred adsorbent media is activated carbon. Preferably, the filter assembly includes about 30 mg to about 200 mg of the adsorbent.

By “activated carbon” is meant any porous, high surface area form of carbon. Activated carbon can be derived via thermal treatment of any suitable carbon source. The activation treatment typically increases the porosity, and activated carbon can be provided with a wide range of pore sizes or the pore sizes can be controlled to provide a desired pore size distribution.

In a preferred embodiment, the carbon is in the form of granules and the like. Preferably, the carbon of the preferred embodiment is a high surface area, activated carbon, for example a coconut shell based carbon of typical ASTM mesh size used in the cigarette industry or finer. A particularly preferred activated carbon is commercially available from PICA USA, Inc., Truth or Consequences, New Mexico. The activated carbon could also be manufactured via the carbonization of coal, wood, pitch, peat, cellulose fibers, lignite and olive pits. Carbonization is usually carried out at elevated temperatures, e.g., 400-1000° C. in an inert atmosphere, followed by activation (i.e., calcining) under reducing or oxidizing conditions.

In a preferred embodiment, the activated carbon can be in the form of beads. In other embodiments, the activated carbon can be in the form of granules and/or fibers. Preferably, the activated carbon is adapted to adsorb constituents of mainstream smoke, particularly, those of the gas phase including aldehydes, ketones and other volatile organic compounds, and in particular 1,3-butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, styrene, acetaldehyde and hydrogen cyanide.

In other embodiments, the carbon can be in the form of carbon on tow and/or carbon paper.

Most preferably, the activated carbon can comprise granulated particles ranging in size from about 100 microns to about 5 mm. In an embodiment, the particles of activated carbon have an average size of from about 0.2 to 2 mm (e.g., about 200, 500, 1000 or 2000 microns).

Activated carbon beads contained in the filter assembly preferably range in size from 0.20 mm to about 0.70 mm, as described in U.S. Patent Application Publication No. 2003/0154993, the entire content of which is incorporated herein by reference.

Preferably, activated carbon can have any desired pore size distribution that comprises pores such as micropores, mesopores and macropores. The term “microporous” generally refers to such materials having pore sizes of about 20 Angstroms or less while the term “mesoporous” generally refers to such materials with pore sizes of about 20-500 Angstroms.

In an embodiment, the activated carbon can be selected to have an appropriate surface area to preferentially adsorb and/or absorb targeted constituents from smoke. For example, the preferred activated carbon typically has a surface area greater than about 50 m²/g (e.g., at least about 100, 200, 500, 1000 or 2000 m²/g). Typically, the absorptive capacity of the activated carbon increases with increasing surface area. Furthermore, surface area typically increases with decreasing particle size. When used as cigarette filter media, however, carbon particles having a small particle size may pack together too densely to permit smoke to flow through the filter with desired resistance to draw (RTD) during smoking. On the other hand, if the particle size is too large there may be insufficient surface area to accomplish the desired degree of filtration. Therefore, such factors can be taken into account in selecting carbon particles suitable for filtration of mainstream and/or sidestream smoke.

Preferably at least some, if not all of the adsorbent is flavor-bearing or otherwise impregnated with a flavor so that the adsorbent is adapted not only to remove one or more gas phase smoke constituents from smoke, but also to release flavor into the mainstream smoke stream. For example, flavor can be added to activated carbon by spraying flavorant upon a batch of activated carbon in a mixing (tumbling) drum or alternatively in a fluidized bed with nitrogen as the fluidizing agent, wherein flavorant may then be sprayed onto the carbon in the bed.

Preferably, the randomly-oriented fibers are cellulose acetate fibers. In another embodiment, the randomly-oriented fibers are polyester fibers, polypropylene fibers, and the like. In an embodiment, the randomly-oriented fibers can be woven and/or non-woven where the fibers are randomly joined together.

In a preferred embodiment, the fibers have a Y-shaped cross-section. In other embodiment, the fibers can have a semi-open shape or cross-section with an open void such as the fibers disclosed in U.S. Pat. No. 6,919,105, U.S. Pat. No. 6,913,784, and/or U.S. Pat. No. 6,907,885, the disclosures of which are incorporated herein by reference.

As seen in FIG. 2, preferably, the buccal end 20 of the filter assembly 10 is preferably in the form of a plug 16 of randomly-oriented fibers 14. Preferably, the plug 16 is positioned downstream of the adsorbent 12, held in cavity 15, to prevent adsorbent particles, having a size of about 0.1 micron to about 10 microns, from traveling through the channels between the fibers and/or migrating along the fibers as in prior filter assemblies using axially oriented fibers. In a preferred embodiment, a plug 25 of axially oriented fibers 30 is upstream of the adsorbent 12.

In use, smoke is drawn first through the plug 25 of axially oriented fibers 30, through the adsorbent 12, and downstream through the plug 16 of randomly-oriented fibers 14. Because of the random orientation of the downstream plug 16 of fibers, the adsorbent particles are not able to travel through the channels between the fibers and/or migrate along the fibers, resulting in the mechanical capture of the adsorbent particles entrained in mainstream smoke.

In another embodiment, as illustrated in FIG. 3, the filter assembly 10 includes a portion of an adsorbent 12 in a cavity 15. On each side of the portion of adsorbent 12 lies a plug 16 of randomly-oriented fibers 14.

In yet another embodiment, as illustrated in FIG. 4, the filter assembly 10 includes a cavity 15 filled with an adsorbent 12. Preferably, a plug 16 of randomly-oriented fibers 14 is located immediately downstream of the cavity 15 filled with the adsorbent 12. Preferably, a plug 25 of axially oriented fibers 30 is located immediately upstream of the cavity 15. Also preferably, a plug 25 of axially oriented fibers 30 is located immediately downstream of the plug 16 containing randomly-oriented fibers 14.

As seen in FIG. 5, the filter assembly 10 is adapted to be incorporated in a smoking article 50.

The term “smoking article” includes cigarettes, cigars, pipes, and cigarillos. Non-traditional cigarettes such as cigarettes for electrical smoking systems, as described in commonly-assigned U.S. Pat. Nos. 6,026,820; 5,988,176; 5,915,387; and 5,499,636, are also included in the definition of smoking articles or cigarettes generally.

Preferably, the smoking article is a cigarette. The cigarette may contain tobacco material and a filter. In an embodiment, the cigarette may also contain at least one sorbent. A traditional cigarette typically contains two sections, a tobacco-containing portion sometimes referred to as the tobacco rod, and a filter portion which may be referred to as the filtration zone. Tipping paper typically surrounds the filter, which forms the buccal end of the cigarette. The tipping paper overlaps with the tobacco rod in order to hold the filter and tobacco rod together. The tobacco rod or tobacco containing element of the cigarette includes the paper wrapper in which the tobacco is wrapped and the adhesive holding the seams of the paper wrapper together. The tobacco rod has a first end which is integrally attached to the filter and a second end which is lit or heated for smoking the tobacco. When the tobacco rod is lit or heated for smoking, the smoke travels from the lit end downstream to the filter end of the tobacco rod and further downstream through the filter.

The following example is given to illustrate embodiments of the filter and should not be construed to limit the scope of such embodiments.

EXAMPLE 1

A 6 mm cellulose acetate plug consisting of randomly oriented cellulose acetate fibers is placed downstream of a cavity filled with 110 mg of activated carbon to form a filter.

Using filters configured as in Example 1 and a control plug-space-plug filter made with two plugs of axially oriented cellulose acetate fibers, the potential for activated carbon particles breakthrough was measured under non-lit dry puff conditions using a laser light scattering particle counter (Met-One Laser Particle Counter Model 237B: Hach Ultra Analytics, Richmond, Calif.).

In testing the filters for carbon particle breakthrough, a laser light scattering particle counter was placed next to a cigarette holder aligned with the air flow through the cigarette. The filter was inserted into a cigarette filter holder to a depth of approximately 9±1 mm and machine puffed under non-lit (dry-puff) conditions using a 55 ml/puff; 2 second puff duration; 12 puffs/cig profile.

TABLE 1 Number of particle breakthrough (particle size >0.3 μm) AVG SD Filter 1 Filter 2 Filter 3 Filter 4 Filter 5 Filter 6 Filter 7 Filter 8 Test#1 251 522 351 167 47 22 31 86 50 38 Test#2 198 384 187 53 47 51 54 40 78 64 Control 1097 225 1010 1429 1155 1102 1087 738 1395 1395

Table 1 illustrates the results of the tests and compares filters constructed according to Example 1 (Test #1 and #2) with traditional plug-space-plug filters having a cavity filled with activated carbon and a plug of axially-oriented cellulose acetate fibers located both upstream and downstream of the activated carbon (Control).

Test #1 filters, constructed according to Example 1, containing randomly-oriented cellulose acetate fibers showed an average carbon particle breakthrough of about 251 particles per cigarette. The particle breakthrough ranged from about 22 particles to about 351 particles per cigarette, which is a significant reduction from the control cigarette filters.

Test #2 filters, constructed according to Example 1, showed an average carbon particle breakthrough of about 198 particles per cigarette. The particle breakthrough ranged from about 40 particles to about 187 particles per cigarette, which is a significant reduction from the control cigarette filters.

In contrast, the control filter, not including randomly-oriented cellulose acetate fibers, showed an average carbon particle breakthrough of about 1097 particles per cigarette. Thus, it is apparent that the use of randomly-oriented cellulose acetate fibers in a filter significantly reduces carbon particle breakthrough during smoking.

It will be understood that the foregoing description is of the preferred embodiments, and is, therefore, merely representative of the articles and methods of manufacturing the same. It can be appreciated that variations and modifications of the different embodiments in light of the above teachings will be readily apparent to those skilled in the art. Accordingly, the exemplary embodiments, as well as alternative embodiments, may be made without departing from the spirit and scope of the articles and methods as set forth in the attached claims. 

1. A filter assembly for a smoking article comprising: an adsorbent including smoke entrainable adsorbent particles contained within the filter, and a plug including randomly-oriented fibers located downstream of said adsorbent, wherein said plug including randomly-oriented fibers provides reduced adsorbent particle breakthrough.
 2. The filter assembly of claim 1, wherein said plug including randomly-oriented fibers is located immediately downstream of said adsorbent.
 3. The filter assembly of claim 1, wherein said plug including randomly-oriented fibers is about 3 mm to about 10 mm in length.
 4. The filter assembly of claim 1, wherein filter assembly contains about 30 mg to about 200 mg of said adsorbent.
 5. The filter assembly of claim 1, wherein said adsorbent comprises carbon on tow, carbon paper, and/or carbon beads, granules particles, and the like in a cavity.
 6. The filter assembly of claim 1, wherein said filter assembly is a plug-space-plug filter, and wherein said adsorbent includes beaded carbon located in the space and the plug of randomly-oriented fibers includes randomly-oriented cellulose acetate fibers incorporated in the downstream plug of the plug-space-plug filter.
 7. The filter assembly of claim 1, wherein said filter assembly includes at least one plug of axially-oriented fibers upstream and/or downstream of said adsorbent and wherein said at least one plug of axially-oriented fibers is incorporated in one or more filter segments included in said filter assembly in an amount sufficient to adjust the length of said filter assembly.
 8. A cigarette comprising the filter assembly of claim 1 attached to a tobacco rod, wherein an outer surface of said plug including randomly-oriented fibers is in contact with tipping paper attaching the filter assembly to the tobacco rod.
 9. The filter assembly of claim 1, wherein said adsorbent is selected from the group consisting of molecular sieve, carbon, and combinations thereof.
 10. The filter assembly of claim 1, wherein said smoke entrainable adsorbent particles range in size from about 0.1 microns to about 10 microns.
 11. A smoking article comprising: a tobacco rod; and a filter assembly including an adsorbent including smoke entrainable adsorbent particles and plug of randomly-oriented fibers, wherein said plug of randomly-oriented fibers provides reduced breakthrough of said particles.
 12. The smoking article of claim 11, wherein said plug of randomly-oriented fibers is located downstream of said adsorbent in the filter assembly.
 13. The smoking article of claim 11, wherein said adsorbent is selected from the group consisting of molecular sieve, carbon, and combinations thereof.
 14. The smoking article of claim 13, wherein said carbon comprises activated carbon on tow, carbon paper, and/or carbon beads, granules particles, and the like in a cavity
 15. The smoking article of claim 11, wherein said adsorbent is included in said smoking article in an amount of about 30 mg to about 200 mg and wherein said adsorbent particles range in size from about 0.1 microns to about 10 microns.
 16. The smoking article of claim 11, wherein said plug of randomly-oriented fibers includes randomly-oriented cellulose acetate fibers, polyester fibers, and/or polypropylene fibers and wherein said plug including randomly-oriented fibers is about 3 mm to about 10 mm in length.
 17. The smoking article of claim 11, wherein said filter assembly further includes one or more plugs of axially-oriented fibers upstream and/or downstream of said adsorbent and wherein said one or more plugs of axially-oriented fibers are included in said filter assembly in an amount sufficient to adjust the length of said filter assembly.
 18. A method of making a filter comprising: placing plugs of 2-up axially-oriented fibers in spaced apart relationship; placing plugs including randomly-oriented fibers between the 2-up plugs such that cavities are formed at upstream and downstream ends of every other 2-up plug; placing an adsorbent including smoke entrainable adsorbent particles in the cavities; and cutting every other of said plugs of 2-up axially-oriented fibers centrally to form 2-up filter assemblies.
 19. The method of claim 18, further including attaching a tobacco rod to each end of said 2-up filter assemblies and cutting said 2-up filter assemblies centrally to form complete cigarettes.
 20. A method of treating mainstream tobacco smoke comprising: contacting said mainstream tobacco smoke with a sorbent; and contacting said mainstream tobacco smoke with randomly-oriented fibers. 